The invention generally relates to pressure protection for a control chamber of a well tool.
A well tool may be remotely controlled from the surface of a well using one of many different control schemes. One type of control involves the use of a control chamber, which may be pressurized (via a control line, for example) to change the state of the tool.
As a more specific example, the tool may be a ball valve, and the control chamber may be pressurized for purposes of closing the valve. The ball valve typically includes a ball valve element that controls the flow of well fluid through a main well fluid passageway of the valve. The control chamber typically is located in a housing of the tool, which surrounds the well fluid passageway, and a seal may isolate the control chamber from the main passageway.
During normal operation, the pressure inside the control chamber remains within a range that may be significantly below the pressure of the well fluid. However, because there is a possibility that the seal that is supposed to isolate the control chamber from the well fluid may leak, the control chamber typically is designed to withstand the higher well pressure. Such a design typically means that the housing of the control chamber is made significantly thicker than would otherwise be needed to withstand the lower control chamber pressure. In general, a thicker housing translates into a smaller cross-sectional area for the well fluid passageway of the tool.
Thus, there is a continuing need for better ways to safeguard a well tool against a seal leak.